A known cooling system suitable for use on board an aircraft comprises a central cold producing device which is thermally coupled to a cold carrier fluid circuit in order to carry off heat from a plurality of heat loads connected, in parallel, to the cold carrier fluid circuit. The heat loads may be at different temperature levels, depending on the operating state, so that the heat transmission from the heat loads to the cold carrier fluid circuit must take place at different temperature levels. In order to ensure proper functioning of the entire system, the operating temperature level of the cold producing device must therefore always be selected such that heat loads which are at a low temperature level are also sufficiently cooled. Consequently, the cold producing device must be operated at an energetically unfavourable low operating temperature level and therefore at a relatively poor efficiency.
A further known cooling system for cooling heat loads on board an aircraft comprises a first cold carrier fluid circuit, which carries off heat from heat loads which are at a low temperature level to a cold producing device. The cold producing device transmits the heat, carried off by the first cold carrier fluid circuit, to a second cold carrier fluid circuit, which serves to carry off heat from heat loads which are at a relatively high temperature level. A heat exchanger, which gives off to the surroundings the heat to be carried off from the entire system, is arranged in the second cold carrier fluid circuit. In order to ensure proper functioning of the entire system at high ambient temperatures as well, the second cold carrier fluid circuit must be maintained at a relatively high temperature level. For this reason, it is necessary to operate the cold producing device at an energetically unfavourable high operating temperature level on the side giving off heat and thus at a relatively poor efficiency. Owing to a technical limitation of the maximum operating temperature of the cold producing device and of further heat loads coupled into the second cold carrier fluid circuit, proper operation of the entire system at very high ambient temperatures can no longer be ensured.